Just because Christ is now synonymous with the Holy Spirit....
Why might it appear that way? Because you cannot see Him with your eyes?
Or because He teaches us and reminds us of what Jesus said? Because He testifies of Jesus?
John 14:26 But the Comforter, which is the Holy Ghost, whom the Father will send in my name, he shall teach you all things, and bring all things to your remembrance, whatsoever I have said unto you.
John 15:26 But when the Comforter is come, whom I will send unto you from the Father, even the Spirit of truth, which proceedeth from the Father, he shall testify of me:
Jesus has sent Him and what does He do?
John 16:7 Nevertheless I tell you the truth; It is expedient for you that I go away: for if I go not away, the Comforter will not come unto you; but if I depart, I will send him unto you. 8 And when he is come, he will reprove the world of sin, and of righteousness, and of judgment: 9 Of sin, because they believe not on me;
He shall not "speak of Himself". Is that proof the Holy Spirit and Jesus Christ are "synonymous" or proof of the ONE GOD in three persons? I guess it depends on what you mean by synonymous.
John 16:13 Howbeit when he, the Spirit of truth, is come, he will guide you into all truth: for he shall not speak of himself; but whatsoever he shall hear, that shall he speak: and he will shew you things to come. 14 He shall glorify me: for he shall receive of mine, and shall shew it unto you. 15 All things that the Father hath are mine: therefore said I, that he shall take of mine, and shall shew it unto you.